Diurnal variations in bacterial numbers and fluid parameters in ruminal contents of animals fed low- or high-forage diets

Abstract

Differential carbohydrate media and anaerobic replica plating techniques were used to assess the degrees of diurnal variations in the direct and viable cell counts as well as the carbohydrate-specific subgroups within the mixed rumen bacterial populations in cattle fed maintenance (metabolizable energy) levels of either a high-forage or a high-concentrate diet once daily. The rumen was sampled at 1 h before feeding and 2, 4, 8, 12, and 16 h after feeding, and selected microbiological parameters of the isolated bacterial populations were assessed. Corresponding samples of ruminal fluid were assayed for fermentation acids, carbohydrate, ammonia, and pH changes. The data showed that regardless of diet, total bacterial numbers remained fairly constant throughout the day. The number of viable bacteria declined 40 to 60% after feeding and then increased to a maximum at 16 h postfeeding. Changes occurred in the carbohydrate-specific subgroups within the bacterial populations, and some of the changes were consistent with a predicted scheme of ruminal feedstuff carbohydrate fermentation. Regardless of diet, however, soluble-carbohydrate-utilizing bacteria predominated at all times. Xylan-xylose and pectin subgroups respectively comprised about one-half and one-third of the population when the high-forage diet was given. These subgroups, along with the cellulolytics, constituted lesser proportions of the population when the high-concentrate diet was given. The cellulolytic subgroup was the least numerous of all subgroups regardless of diet but followed a diurnal pattern similar to that predicted for cellulose fermentation. There were few diurnal variations or differences in bacterial cell compositions and ruminal fluid parameters between diets. The observed similarities and dissimilarities of the rumen bacterial populations obtained when the two diets were given are discussed. The data are consistent with the versatility and constancy of the rumen as a stable, mature microbial system under the specific low-level feeding regimens used.

Effects of Amount and Availability of Starch on Amylolytic Activity of Ruminal Solid-Associated Microorganisms

“…The evolution of the amylase activity of SAM with time after feeding is in agreement with the results of Martin et al (1993), and is the opposite of that observed for the activities of enzymes involved in the degradation of plant cell wall structural polysaccharides for this microbial population (Williams et al 1989 ;Martin et al 1993). Amylolytic bacteria are numerically predominant in the rumen in the initial stages of the postprandial period, when the proportion of bacteria utilising structural plant cell wall polysaccharides is lowest (Leedle et al 1982). During the Ðrst hours after feeding, ingested starch would be rapidly digested whereas the most e †ective breakdown of plant cell wall polysaccharides would occur at later stages of the postprandial period (Leedle et al 1982).…”

“…Amylolytic bacteria are numerically predominant in the rumen in the initial stages of the postprandial period, when the proportion of bacteria utilising structural plant cell wall polysaccharides is lowest (Leedle et al 1982). During the Ðrst hours after feeding, ingested starch would be rapidly digested whereas the most e †ective breakdown of plant cell wall polysaccharides would occur at later stages of the postprandial period (Leedle et al 1982).…”

“…The stimulation of amylase activity may be related to a modiÐcation of the microbial population induced by barley supplementation (Dehority and Orpin 1988). Proportions of amylolytic and lactate-utilising bacteria in the rumen are increased by supplementation of forage diets with cereals (Mackie and Gilchrist 1979 ;Roxas 1980 ;Leedle et al 1982). The increase in SAM amylolytic activity may also be attributed to an increase in amylase synthesis.…”

Rumen microbial variation and nutrient utilisation in mithun (Bos frontalis) under different feeding regimes

“…Traditional cultivating and enumerating methods of rumen microbes (Leedle et al, 1982) are based on the use of typical anaerobic culture techniques, which are laborious and cumbersome. Further, most of the microbes in natural ecosystems are unculturable by the conventional methods (Ward et al, 1990).…”

Comparative studies of microbial populations in the rumen, duodenum, ileum and faeces of lactating dairy cows

“…Culture-based analyses (Mackie and Gilchrist 1979;Leedle et al 1982) and cultivation-independent surveys (Tajima et al 2000(Tajima et al , 2001Kocherginskaya et al 2001;Klieve et al 2003;Wright et al 2004;Larue et al 2005) have indicated that ruminal micro-organisms are affected by diet. In this study, energy levels were similar in the two diets, but there were postruminal differences in the amount of available nitrogen.…”